insights: FK constraint violated on insight dirty queries table

Created by: coury-clark

"failed to purge orphaned frontend series: ERROR: update or delete on table "insight_series" violates foreign key constraint "insight_dirty_queries_insight_series_id_fkey" on table "insight_dirty_queries" (SQLSTATE 23503)"

Caused by missing cascade when orphaned series are attempted to be cleaned up during the 10 minute sync jobs. https://sourcegraph.com/github.com/sourcegraph/sourcegraph@main/-/blob/enterprise/internal/insights/discovery/discovery.go?utm_product_name=GoLand&utm_product_version=GoLand#L316:6